Release mechanism

ABSTRACT

The present invention relates to a release mechanism ( 1 ) for use in supporting a load ( 6 ) from a crane. The release mechanism ( 1 ) comprises a remotely operable release hook ( 2 ) for supporting by a cable ( 4 ) a load ( 6 ). The hook ( 2 ) is provided with an ejector lever ( 8 ) for releasing the cable from the hook ( 6 ) upon actuation of the ejection lever ( 8 ). Connected above the hook ( 2 ) by a cable link ( 10 ) is a control unit ( 12 ) arranged for controlling the ejector lever ( 8 ) on the hook ( 2 ). The control unit ( 12 ) and the ejector lever ( 8 ) are connected together by a communication cable ( 14 ) carrying pressurised hydraulic fluid. The control unit and the hook are substantially spaced apart.

The present invention relates to a release mechanism suitable for usewith lift or crane hooks but not exclusively. The invention relates alsoto a hook for use with the release mechanism and to a control system foruse therewith.

Release mechanisms for use with crane hooks and the like are generallywell known. There are essentially two different types of releasemechanism for use with hooks—the self-releasing type arranged forautomatically releasing the load on a hook upon deposition of the loadon the ground and manually operable release mechanisms which release aload only upon being activated by an operator. The former automaticallyreleasing mechanisms have the disadvantage that they release a load assoon as it is placed on the ground and thus for example, if the load isin the wrong place, it has to be placed back onto the crane hook beforeit can be moved. This is time consuming and in certain conditions, forexample off-shore drilling operations, potentially very dangerous tooperators. Such automatically releasing mechanisms are known from DEPatent No. 2757321, FR Patent No. 2411795, SU Patent No. 578257,International Publication No. WO 86/07582 and U.S. Pat. No. 5,178,427.

The latter type of release mechanism which are frequently arranged forremote operation have the advantage over automatically releasingmechanisms that they will only release a load when instructed to do soby an operator and thereby avoid unintentional disconnection. UK PatentPublication No. 2293407A discloses a crane hook having a remotelycontrolled ejection lever. A particular disadvantage of the releasemechanism disclosed therein is that there is required a more or lesslarge shank housing to house a motor; an hydraulic pump driven by saidmotor; a power supply for said motor; an hydraulic cylinder/ram drivenby the hydraulic pump and the various control circuitry for the remoteoperation of the ejection lever portion of the hook. Both types ofrelease mechanism might typically be approximately 1 m in length and lmin diameter and weigh 565 kg and do not lend themselves to use inoff-shore oil and gas exploration applications as it will be appreciatedthat such a large and heavy hook may swing about and result in damageunder adverse weather and other operating conditions to installationsand personnel securing a load to be carried by the hook.

Furthermore, conventional known hooks are generally in the form of moreor less large cast or forged one-piece bodies containing an ejectionlever. One disadvantage of such one-piece bodies is that they are notpossible to repair insofar as they cannot be disassembled. Furthermore,the arrangement by which the ejector lever is operated, i.e. a hydraulicram together with the one-piece construction, means that such hooks aregenerally large with the hydraulic ram mounted externally as in GB2293407A.

Additionally, such one-piece hooks which have a centrally mountedejection lever cannot meet increasingly stringent national, regional andinternational standards in, for example, the United Kingdom and De NorskVeritas rules relating to offset loading. Offset loading is where onemay have different loadings on the hook on each side of the centrallymounted ejection lever due to a load not being lifted centrally or bythe load swinging as may happen in use on off-shore application.

It is an object of the present invention to avoid or minimise one ormore of the foregoing disadvantages.

In a first respect the present invention provides a release mechanismsuitable for use in releasing remotely a load supported on a hook or thelike which mechanism comprises a discrete load supporting means providedwith ejector means formed and arranged for selectively ejecting a saidload supported thereby and discrete control means formed and arrangedfor controlling said ejector means on said load supporting means;characterised in that said load supporting means is substantially spacedapart and depends from said control means by an elongate support linkand said control means and said ejector means are connected together bya communication means whereby in use a load may be secured to said loadsupporting means by an operator with said control means of the releasemechanism substantially remote from said operator.

Thus, with a release mechanism according to the present invention a loadmay be secured thereto in a substantially safer way than previousdesigns of automatic and remotely releasable mechanisms have allowed.

Preferably, said control means is provided in a control means housingwhich includes power supply means for driving said ejector means.Preferably, said power supply means is in the form of compressedpressurised hydraulic fluid contained within an accumulator bladder andsaid ejector is in the form of hydraulic ram in spaced apartcommunication with said control means whereby said control means cancontrol the flow of pressurised hydraulic fluid from said accumulator tosaid spaced apart ejector means. Preferably said control means is in theform of valve means formed and arranged in a first open position topermit pressurised fluid to pass from said accumulator to said ejectormeans for operation thereof and in a second closed position to preventpressurised fluid passing to said ejector means and thereby operatingsaid ejector means for ejecting a load supported on said load supportingmeans. Preferably, said communication means in the form of an elongateflexible hydraulic pipe of generally known type and construction.

In its simplest form, the volume of hydraulic fluid being transferredfrom said accumulator to said ejector is a generally fixed volume.Preferably though, and so as to provide for a standby or redundancyeventuality in the situation where for example there is a partial lossof hydraulic fluid, the accumulator bladder is so formed and arrangedwith a capacity to store a plurality of charges of pressurised fluid, inthe range of from two to ten charges for example five charges, eachcharge being sufficient to operate the ejector means once. Preferably,the charging of the accumulator is effected by a self generating powerlift cylinder formed and arranged within the control means whereuponupward movement of the control means by, for example a crane, in use ofthe release mechanism, and lifting a load loaded onto said loadsupporting means causes said cylinder to stroke within the control unitand to pressurize fluid into said accumulator. Preferably, said cylinderhas a full stroke in the range of from 175 mm to 230 mm and one fullstroke of the cylinder is sufficient to provide a plurality of charges,for example five to seven charges, each charge being sufficient tooperate said ejection means once. Desirably, a partial stroke of thecylinder, for example a stroke of 35 mm, is sufficient to provide one totwo charges, each charge being sufficient to operate the ejection meansonce.

Preferably, there is provided a hydraulic fluid reservoir to supplyfluid to be pressurised in said cylinder. Preferably, said reservoir isin the form of an annular tank surrounding said accumulator so as toreduce the overall length of the control means of the release mechanismaccording to the invention.

Preferably, said valve means is actuated by a solenoid type switch whichis switched on and/or off by a hand held remote control transmitterusing infra-red acoustic (for underwater applications) or radio signalsto transmit a control signal to said control means for operation of saidsolenoid valve. The remote control transmitted may be of the threechannel, two switch high security radio transmitter type and includes areceiver/decoder so that the receiver will decode received signals andoperate only if the received signals are correct. Thetransmitter/receiver may be pre-set to any one of a multiplicity ofseparate radio frequencies and signal codes according to a user'srequirements. This feature is particularly useful where several releasemechanisms according to the invention are in use and it is required tooperate them selectively and independently of each other. The controlmeans is provided with an aerial/antenna to pick up and receive signals.Preferably, said receiver/decoder is arranged with an explosion proofcontainer. Preferably, said control means is formed and arranged with anautomatic reset feature whereby once the release mechanism has beenactuated, and a load released, the release mechanism reverts to a readyto operate state.

As the control means of the present invention utilise preferably asolenoid type switch which requires only a small power source, there isobviated the need for large batteries or power supplies to drivehydraulic pumps as with existing known release mechanisms and theproblems associated therewith. Preferably, there is provided in saidcontrol means housing a battery housing formed and arranged with aremovable cover to facilitate recharging or replacement of a batterycontained therein.

Preferably, said load supporting means is in the form of an inverted ‘U’shaped hook and said ejector means is in the form of a lever formed andarranged upon actuation of the ejector means to push a cord or cable onwhich a load is slung to be pushed from within the hook up and outthereof for release from said hook.

Desirably, said discrete load supporting means is in the form of arelease hook comprising a body portion having left and right handsections releasably connected together and having therebetween at alower hook portion of said body an ejection means in the form of a leverformed and arranged to move from a first substantially retractedposition between said left and right hand sections to an extendedejecting position between said left and right hand sections so as topush a cord or cable on which a load is slung from within the hook upand out thereof for release from said hook. Said left and right handsections of said body portion are preferably connected together byreleasable fasteners such as bolts and located relative to each other bystuds or dowels.

Preferably, and so as to reduce the overall size of the release hook,said left and right hand sections of said body portion house thereinsaid hydraulic ram for driving said lever from said retracted positionto said ejecting position. Desirably and again to reduce the overallsize of the release hook, said hydraulic ram comprises a piston portionand a cylinder portion, said piston portion being mounted about atrunnion end thereof to an upper body portion of said hook and saidcylinder portion being fixed to a lower portion of said ejection means,said cylinder portion moving relative to said fixed piston portionwhereby in use said hydraulic ram, with said ejector means in saidretracted position, starts from an extended length and retracts underthe action of pressurised hydraulic fluid acting on the underside ofsaid piston to an extended position, so as to drive said cylinderportion with respect thereto and thereby to drive said ejector meansfrom said retracted position to said ejecting position.

Desirably, said release hook is releasably connected to said elongatelink means by means of a shackle, preferably a bow or ‘D’ shackle.

Preferably, said lower hook portion of said left and right hand sectionsof said release hook have a surface profile formed and arranged tocompliment the surface profile of a shackle loop supporting a load to belifted by said discrete load supporting means whereby in use the loadexerted on said lower hook portion of said left and right hand sectionsis generally evenly distributed therebetween even when the load isexerting an offset load such as that found, for example, when liftingelongate loads such as pipework.

Preferably, where it is required to lift very long elongate loads suchas, for example, offshore pipework, there is provided a second discreteload supporting means provided with an ejection means, said second loadsupporting means being spaced apart from the other load supporting meansand releasbly mounted on a boom member, desirably an extensible boommember. Desirably, said communication means is formed and arranged toconnect together said control means and said two spaced apart loadsupporting means. Where it is required to lift very large loads, theremay be provided three or more load supporting means releasably mountedon, for example, a triangular or rectangular frame, all of said loadsupporting means being connected to said control means whereby anoperator can selectively eject a said load supported by said three ormore load support means.

Preferably, said elongate support link connecting said load supportingmeans and said control means is in the form of a more or lesssubstantial flexible steel cable or rope or interlinked chain. Saidelongate support link may be of any length depending on the particularapplication but has a length in the range of from 1 m to 5 m, preferably3 m, so as to keep the control means portion of the release mechanism asafe distance away from an operator. Said elongate support link may beprovided with tensile stress measuring means such as a potentiometerformed and arranged with said control means so that in the event of aload that is too heavy for the crane in use of the release mechanism tolift safely, the release mechanism may be actuated and/or audible and/orvisual alarm means actuated.

Said control means is provided with coupling means formed and arrangedfor coupling with said elongate support link. Preferably, said couplingmeans is in the form of a shackle, desirably a ‘D’-shaped shackleconnected to a connecting rod which is connected to a piston of saidcontrol means hydraulic ram. Desirably said connecting rod extendsoutwardly of the control means housing and is mounted in guides, forexample bearing flats, formed and arranged to prevent rotation of saidconnecting rod and a load connected thereto via said load supportingmeans with respect to said control means housing. Desirably, saidcontrol means housing comprises a plurality of desirably cylindricalsections screwably connected together so as to facilitate manufacture,assembly/disassembly and repair of the control means. Preferably, saiddesirably cylindrical sections are provided with anti-rotation lockingscrews to prevent said sections of said housing unscrewing in use.

Further preferred features and advantages of the present invention willappear from the following detailed description given by way of exampleof some preferred embodiments illustrated with reference to theaccompanying drawings in which:

FIG. 1 is a schematic layout of the control means circuitry of therelease mechanism according to the invention;

FIG. 2 shows the release mechanism in use on a crane hook supporting aload;

FIG. 3 shows a cutaway side view of the hook part of the releasemechanism;

FIG. 4 is a sectional side view of a second embodiment of releasemechanism according to the invention;

FIG. 5 is a sectional side view of a control unit of the embodiment inFIG. 4;

FIG. 6 is an enlarged side view of the hook part of the releasemechanism shown in FIGS. 4 and 5;

FIG. 7 is front view of the hook shown in FIG. 6; and

FIG. 8 is a schematic layout of the control means of the releasemechanism shown in FIGS. 4-7.

A release mechanism, generally indicated by reference number 1, for usein supporting a load from a crane (not shown) is shown in FIG. 2. Therelease mechanism comprises a remotely operable releasable hook 2 forsupporting by a cable 4 a load 6. The hook 2 is provided with an ejectorlever 8 (see also FIG. 3—which is shown in larger scale for improvedclarity) for releasing the cable from the hook 6 upon actuation of theejector lever 8. Connected above the hook 2 by a three meter long cablelink 10 is a control unit 12 arranged for controlling the ejector lever8 on the hook 2. The control unit 12 and the ejector lever 8 areconnected together by a communication cable 14, which in the case of theembodiment described is an hydraulic cable. The top portion 16 of thecontrol unit 12 is secured through a clevis pin 20 to a crane cable 22.

In use, an operator (not shown) would connect the cable 4 of a load 6onto the hook 2 with the control unit 12 above and a safe distance awayfrom the operator. When the load is secured, the crane can be operatedin the generally known way so as to lift the load 6 clear of the ground18 such that the load can be moved to a new position. Once the load islowered into its new position, an operator (who could be the craneoperator) can by using a hand held remote radio transmitter unit 24instruct the control unit 12 to operate the ejector lever 8 on the hook2 so as to release the load support cable from the hook 2.

The control unit 12 comprises a control unit housing 26 for containingin an intrinsically safe environment the control elements of the controlunit 12 which will now be described with reference to the schematiclayout shown in FIG. 1.

The control unit housing 26 contains an hydraulic fluid reservoir 28connected on one side through a non-return valve 30 to a cylinder 32containing a spring 34 biased piston 36. The lower end 38 of this piston36 is connected to the link cable 10 (see also FIG. 2) from whichdepends the hook and the load (shown by arrow ‘A’). The cylinder 32 isconnected hydraulically through a further non-return valve 40 to abladder accumulator 42 which is in turn connected to a solenoid operablevalve 44 which is switchable between the communication cable 14 conduitconnected to an hydraulic ram 46 on the ejector lever 8 of the hook 2and, by another conduit 48, the reservoir 28.

In use, when a load 6 is lifted, the first piston 36 contained in thelower end 50 of the control unit 12 is pulled downwards within thecylinder 32 compressing the spring 34 and forcing hydraulic fluid intothe accumulator 42 where it is stored under pressure during the periodof operation of the lift. The non-return valve 30 prevents fluid goinginto the reservoir 28. Once the load has been placed in the requiredposition, an operator holding the hand held transmitter unit 24 sends aradio signal 52 to the control unit 12 where it is received by anantenna 54. This signal 52 is processed by a processor unit (not shown)which causes the solenoid valve 44 to operate so that the pressurisedhydraulic fluid stored in the accumulator 42 passes along thecommunication cable 14 into the hydraulic ram 46 connected to theejector lever 8 on the hook 2. This pressurised fluid causes thehydraulic ram to extend (in the direction of arrow ‘B’—FIGS. 2 and 3)and thereby to push the cable 4 off the hook 2 disengaging the load 6.

As there is now no load applied to the control unit 12, the pistonspring 34 in the control unit cylinder 32 expands and draws fluid fromthe reservoir 28 through the non-return valve 30 and thereby primesitself ready for the next lift.

At the same time, the operator will have sent a second signal 52 to thecontrol unit 12 operating the solenoid so that fluid in the hydraulicram 46 on the hook 2 is returned to the reservoir 28. The hydraulic ram46 includes a biasing spring 56 so that as the ejector lever 8 retractsinto the hook 2 it forces fluid back into the reservoir. The hook 2 andthe release mechanism 1 are then in a primed condition ready for thenext lift.

The link piston 36/cylinder 32 is provided with a safety cutout switchso as to avoid “over-weight” loads being lifted.

The control unit has a length of approximately 2.5 meter, an outsidediameter of ¼ m (250 mm) and a weight of 200 kg.

A second preferred embodiment of release mechanism according to theinvention is shown in FIGS. 4 to 8 and will be described with likereference numbers to those used above to describe the embodiment shownin FIGS. 1 to 3.

The release mechanism, generally indicated also by reference number 1,is for use in loading, lifting and unloading a load (not shown) from acrane (not shown). The release mechanism 1 comprises a remotely operablehook 2 for supporting by a load hook shackle 4 (shown in broken line) aload (not shown). The hook 2 is provided with an ejector lever 8 (seealso FIG. 6—which is shown in larger scale for improved clarity) forreleasing the cable from the hook 6 upon actuation of the ejector lever8. Connected above the hook 2 by a 3 m long cable link 10 is a controlunit 12 (shown partially) arranged for controlling the ejector lever onthe hook 2. The control unit 12 and the ejector lever 8 are connectedtogether by a communication cable 14, which in the case of theembodiment described is a hydraulic cable. The top portion 16 of thecontrol unit 12 is secured through a clevis pin 20 to a crane (notshown).

The mode of operation of the release mechanism 1 is as described abovewith reference to the first embodiment shown in FIGS. 1 to 3.

The control unit 12 comprises a control unit housing 26 for containingin an intrinsically safe environment the control elements of the controlunit 12 which will now be described with the reference to the schematiclayout shown in FIG. 8 and with reference also to the cut-away sidesection of the control unit 12 shown in FIG. 5.

The control unit housing 26, which comprises an elongate cylindricalvessel 27 with end caps 27 a, contains an hydraulic fluid reservoir 28which has an annular form and which is connected on one side throughnon-return valve 30 to a cylinder 32 containing a spring 34 biasedpiston 36. The lower end 38 of this piston 36 is connection to the linkcable 10 (see also FIG. 4) from which depends the hook and a load (shownby arrow “B”). The cylinder is connected hydraulically through a furthernon-return valve 40 to a bladder accumulator 42 which is in turnconnected to a solenoid operable valve 44 which is switchable betweenthe communication cable 14 conduit connected to an hydraulic ram 46 onthe ejector lever of the hook 2 and, by another conduit 48, to thereservoir 28, which surrounds the bladder accumulator 42.

The accumulator 42 has a total capacity of 2.5 liters and is pre-chargedto 225 psi/1550 kN/m², the reservoir is half filled and has a capacityof 2.5 liters. A relief valve 31 is provided between the solenoid valveand the reservoir and is set at 500 psi/3447 kN/m². The hydrauliccircuitry is also provided with a bleed fitting 33 and a fitting 35 forconnection to a test gauge 37.

The solenoid valve 44 is connected by an electrical cable 39 to anelectronic control box 43 which is connected electrically to a battery45 contained in a sealed battery container 47. The battery has a 12 voltdc power supply.

In use, when a load (not shown) is lifted, the first piston 36 containedin the lower end of the control unit 12 is pulled downwards within thecylinder 32 compressing the spring 34 and forcing hydraulic fluid 41into the accumulator 42 where it is stored under pressure during theperiod of operation of the lifting of the load. The non-return valve 30prevents fluid 41 going into the reservoir 28. Once the load has beenplaced in the required position, an operator holding a hand heldtransmitter (not shown) sends a radio signal 52 to the control unitwhich is received by an antenna 54, connected to the electronic controlbox 43. This signal 52 is processed by the processor unit which causesthe solenoid valve 44 to operate so that the pressurised hydraulic fluidstored in the accumulator 42 passes along the communication cable 14into the hydraulic ram connected to the ejector lever 8 on the hook 2(see also FIGS. 4, 6 and 7). This pressurised fluid 41 causes thehydraulic ram 46 to pull the ejector lever 8 upwardly thereby to pushthe ring 4 off the hook 2 to disengage the load.

As there is now no load applied to the control unit, the piston spring34 in the control unit cylinder 32 expands and draws fluid from thereservoir 28 through the non-return valve 30 thereby priming itselfready for the next lift. The electronic control unit is provided with anautomatic reset function so as to reset the solenoid valve so that therelease mechanism is ready for the next lift. The effect of thisautomatic reset function is such that the fluid in the hydraulic ram 46on the hook 2 is returned to the reservoir 26. The hydraulic ram 46 onthe hook (and shown in more detail in FIGS. 6 and 7) includes a biasingspring 56 so that as the ejector lever 8 retracts into the hook 2, fluidflows back into the reservoir 28.

The hook 2, shown in more detail in FIGS. 6 and 7, comprises a left hand58 and right hand 60 portions which form the body 62 of the hook 2. Theleft and right hand body portions contain the hydraulic ram 46 connectedto the ejection lever 8. The left and right hand body portions areconnected together by bolts 64 and dowels 66. The top part 68 of thehydraulic ram 46 is fixed via a trunnion 70 to the top portion of thehook 2. The bottom portion of the ejector lever 8 is connected at 72 tothe lower end cylinder portion of the hydraulic ram 46. Pressurisedhydraulic fluid enters on the underside 74 of the piston portion of thehydraulic ram 46 such that the hydraulic ram 46 pushes the cylinderportion of the ram upwardly thereby drawing up the ejector lever 8 so asto disengage the ring 4 from the hook 2. It will be appreciatedtherefore that, instead of using a hydraulic ram which starts in acontracted state and expands into a deployed elongate state, the overalllength of the hook can be substantially reduced.

As an indication, the height of the hook 2 is approximately 600 mm, thelength of the control unit is approximately 2500 mm and the length ofthe cable link 10 is approximately 3000 mm. The hook has a safe workingload of 12 tonne, the link cable a safe working load of 12 tonne and thecontrol unit a safe working load of 25 tonne. The shackle for connectingtogether the control unit and cable link and the cable link to the hookhave safe working loads of 13 tonne.

Various modification may be made to the above-described embodimentswithout departing from the scope of the present invention. Thus, forexample instead of the control units being connected directly to a hook,there could be provided two spaced apart hooks mounted on either end ofan extensible boom which boom is connected at a centre position to thebottom of the control unit.

What is claimed is:
 1. A release mechanism (1) suitable for use inreleasing remotely a load (6) supported on a hook (4) or the like whichmechanism comprises a discrete load supporting means (2) provided withejector means (8) formed and arranged for selectively ejecting a saidload supported thereby and discrete control means (12) formed andarranged for controlling said ejector means (8) on said load supportingmeans (2), said control means (12) being provided in a control meanshousing (27) which housing (27) includes power supply means (42) fordriving said ejector means (8), said load supporting means (2) beingsubstantially spaced apart and depending from said control means (12) byan elongate support link (10) and said control means (12) and saidejector means (8) being connected together by a communication means(14), and a reservoir (28) to supply pressurised fluid; characterised inthat said power supply means (42) is in the form of a compressedpressurised hydraulic fluid contained within an accumulator bladder (42)and said reservoir (28) is in the form of an annular tank surroundingsaid accumulator bladder (42).
 2. A release mechanism according to claim1 wherein said ejector is in the form of a hydraulic ram (46) in spacedapart communication with said control means (12).
 3. A release mechanismaccording to claim 2 wherein said control means housing (27) contains anexplosion proof housing for housing a control unit (43).
 4. A releasemechanism according to claim 1 wherein said control means is in the formof a valve means (44) formed and arranged in a first open position topermit pressurised fluid to pass from said accumulator (42) to saidejector means (8) for operation thereof and in a second closed positionto prevent pressurised fluid passing to said ejector means (8).
 5. Arelease mechanism according to claim 4 wherein said valve means isactuated between said first and second positions by a solenoid typeswitch (44).
 6. A release mechanism according to claim 1 wherein saidcommunication means (14) is in the form of an elongate flexiblehydraulic pipe.
 7. A release mechanism according to claim 1 wherein saidaccumulator bladder (42) is formed and arranged with the capacity tostore a plurality of charges of pressurised fluid, each one of saidcharges of pressurised fluid being sufficient to operate said ejectormeans at least once.
 8. A release mechanism according to claim 1 whereinthe charging of the said accumulator (42) is effected by a selfgenerating power lift cylinder (32) formed and arranged within saidcontrol means (12) whereby upward movement of the control means causessaid cylinders to stroke and to pressurize hydraulic fluid into saidaccumulator bladder (42).
 9. A release mechanism according to claim 1wherein said control means (12) is operable remotely by a hand heldcontrol transmitter (24).
 10. A release mechanism according to claim 1wherein said load supporting means (2) is in the form of an invertedU-shaped hook and said ejector means (8) is in the form of a leverformed and arranged upon actuation of said ejector means to push a cordor cable on which a load is slung from within the hook up and outthereof for release from said hook (2).
 11. A release mechanismaccording to claim 1 wherein said load supporting means is in the formof a release hook (2) comprising a body portion having left (58) andright (60) hand sections releasably connected together and housingtherebetween at a lower hook portion said ejector means (8).
 12. Arelease mechanism according to claim 11 wherein said ejector means is inthe form of a lever (8) formed and arranged to move from a firstsubstantially retracted position between said left (58) and right (60)hand sections to an extended ejecting position between said left andright hand sections.
 13. A release mechanism according to claim 12wherein said discrete load supporting means (2) houses an hydraulic ram(46) for driving said lever (8) from said retracted position to saidejecting position.
 14. A release mechanism according to claim 11 whereinsaid left (58) and right (60) hand sections of said body portion areconnected together by releasable fasteners (64).
 15. A release mechanismaccording to claim 11 wherein said lower hook portion of said left (58)and right hand (60) sections of said release hook (2) have a surfaceprofile formed and arranged to compliment the surface profile of ashackle loop (4) supporting a load (6) in use of the release mechanism.16. A release mechanism according to claim 1 wherein there is provided asecond discrete load supporting means (2) provided with ejection means(8), said second load supporting means being spaced apart from the otherload supporting means and releasably mounted on a boom member.
 17. Arelease mechanism according to claim 16 wherein said boom member isextensible.
 18. A release mechanism according to claim 1 wherein thereare provided three or more load supporting means (2) connected to saidcontrol means (12).
 19. A release mechanism according to claim 1 whereinsaid elongate support link (10) connecting said load supporting means(2) and said control means (12) is in the form of a substantiallyflexible cable.
 20. A release mechanism according to claim 1 whereinsaid control means housing (27) is provided with guide means formed andarranged to prevent rotation of said control means hydraulic ram (38)with respect to said control means housing (27).